The present invention relates to a method for producing a substrate including a pad formed at one side of a semiconductor substrate and simultaneously insulated from the semiconductor substrate and a penetration electrode formed in the semiconductor substrate at the portion facing the pad, one end part of which is connected to the pad, and simultaneously insulated from the semiconductor substrate.
As prior art substrates, there is a substrate equipped with a semiconductor device (for example, CMOS sensor and memory, etc.) formed on a semiconductor substrate, a pad formed at one side of the semiconductor substrate and electrically connected to the semiconductor device, and a penetration electrode that penetrates the semiconductor substrate at the portion facing the pad, one end part of which is electrically connected to the pad, and a substrate (See FIG. 1) equipped with a pad formed on one side of the semiconductor substrate and electrically connected to a semiconductor chip, and a penetration electrode penetrating the semiconductor substrate at the portion facing the pad, one end part of which is connected to the pad.
FIG. 1 is a sectional view of a prior art substrate.
Referring to FIG. 1, the prior art substrate 200 includes a semiconductor substrate 201, oxidation films 202, 203, a penetration electrode 204, and a pad 205. The semiconductor substrate 201 is a plate-shaped substrate, and a through hole 207 is formed. As the semiconductor substrate 201, for example, a silicon substrate may be used.
The oxidation film 202 is provided so as to cover the surface 201A of the semiconductor substrate 201 and the rear 201B thereof. The oxidation film 203 is provided so as to cover the side of the semiconductor substrate 201 at the portion corresponding to the side of the through hole 207.
The penetration electrode 204 is provided in the through hole 207 having the oxidation film 203 formed thereon. The pad 205 is provided on the upper end part of the penetration electrode 204 and on the oxidation film 202 formed on the surface 201A of the semiconductor substrate 201. The pad 205 is electrically connected to the penetration electrode 204. The pad 205 is a pad electrically connected to a semiconductor chip (not illustrated).
FIGS. 2 to 8 are views showing production processes of a prior art substrate. In FIGS. 2 to 8, components that are identical to those of the prior art substrate 200 are given the same symbols.
Referring to FIGS. 2 to 8, a description is given of a method for producing a prior art substrate. First, in the process shown in FIG. 2, oxidation films 202 are formed so as to cover both sides 201A and 201B of a semiconductor substrate 201. Next, in the process shown in FIG. 3, an opening portion 202A is formed in the oxidation film 202 provided at the rear 201B of the semiconductor substrate 201. The opening portion 202A is formed so as to expose the rear 201B of the semiconductor substrate 201 at the portion corresponding to an area where the through hole 207 is formed.
Next, in the process shown in FIG. 4, a through hole 207 that penetrates the semiconductor substrate 201 is formed by etching in which the oxidation film 202 having the opening portion 202A formed therein is used as a mask. Next, in the process shown in FIG. 5, the semiconductor substrate 201 at the portion corresponding to the side of the through hole 207 is thermally oxidized, the oxidation film 203 is formed on the semiconductor substrate 201 at the portion corresponding the side of the through hole 207.
Next, in the process shown in FIG. 6, a pad 205 is formed on the oxidation film 202 at the portion positioned upward of the through hole 207. Next, in the process shown in FIG. 7, the oxidation film 202 disposed between the pad 205 and the through hole 207 is removed by etching (dry etching or wet etching).
Further, in the process shown in FIG. 8, a penetration electrode 204 is formed by filling up a conductive material in the opening portion 202A shown in FIG. 7 and the through hole 207, thereby producing a substrate 200 (For example, refer to Patent Document 1).
[Patent Document 1] JP-A-No. 2004-95849
However, in compliance with the prior art method for producing the substrate 200, the oxidation film 202 disposed between the pad 205 and the through hole 207 is removed by etching (dry etching or wet etching) after the oxidation film 203 is formed at the semiconductor substrate 201 at the portion corresponding to the side of the through hole 207. Therefore, an etching remainder (residue) occurs at the oxidation film 202 at the portion disposed between the pad 205 and the through hole 207 (in this case, the resistance value between the penetration electrode 204 and the pad 205 is increased), the oxidation film 203 for which etching is not required is etched to thin the thickness of the oxidation film 203 (in this case, defective insulation is brought about between the semiconductor substrate 201 and the penetration electrode 204). Accordingly, there is a problem that the yield of substrates 200 is lowered.